A surgical stapler is a kind of medical instrument which is commonly used in surgery operations for intestinal or other tissue, the performance of the surgical stapler is very important to the success of whole surgery operation. A safety device is generally disposed on the surgical stapler in order to avoid mis-actuating. In prior art, most safety devices on circular staplers are operated manually, that is, when a doctor performs a surgery operation on a patient, the doctor does not release the safety device to perform actuations until he has already finished all the preparation works. But this kind of safety device has deficiencies identified in practice: if the doctor is less experienced, he may release the safety device to perform actuations in surgery operations even though the stapling distance is not in the right range, which leads to unwanted surgery operation results; or if the safety device is forgotten to be locked when replacing the stapler head assembly, it is very likely to grip the actuator trigger, accordingly the staples are shot out of the stapler head assembly, which leads to the failure of the surgery operation; some doctors may give a second actuation so as to avoid incomplete actuating, which results in tissue to be clamped into pieces. Therefore, the “safety device” and “device preventing second actuation” on this kind of stapler have become a research focus for people.
Regarding safety device, U.S. Pat. No. 5,193,731 disclosed a rotatable safety device disposed on an adjusting knob and U.S. Pat. No. 5,350,104 disclosed a safety device which is pivotally connected with a stapler body; both of the above mentioned staplers require the doctor to release the safety device manually when reaching the actuatable position. Chinese patent no. 99229088 disclosed an automatic safety device which is complex in assembling with too many parts and it is very difficult to get reset after being released; Chinese patent no. 99227301 disclosed a safety device by a safety rod propping against a screw rod, but the screw rod can be easily bent with this configuration.
Regarding the second actuation, Chinese patent no. 98121969 disclosed a safety device which can be automatically reset by a spring to prevent second actuation, which has deficiencies that: the spring is disposed outside the stapler body which increases the risk of clamping tissues, similarly the safety device props against the screw rod which can easily cause the screw rod bent. Due to the above mentioned reasons, according to the applicant's knowledge, —currently used staples in practice are not equipped with proper safety device to prevent the second actuation.